History-independent noise-immune modulated transformer-coupled gate control signaling method and apparatus

A circuit, comprising:

• a switching power stage for producing a switched power output at a switching rate and having at least one power switching transistor;
• a switching control circuit for determining a turn-on time and a turn-off time of the at least one power switching transistor at the switching rate, and having an output for providing a modulated control signal having a modulated rate that is greater than the switching rate, and wherein the switching control circuit encodes one or more event types according to relative timing between transitions of the modulated control signal, the event types including a turn-on event that indicates the turn-on time of the at least one power switching transistor, and wherein the switching control circuit stops the transitions of the modulated control signal to conserve power between events;
• a transformer for coupling the output of the switching control circuit to the at least one power switching transistor, whereby the at least one transistor has a gate that is DC isolated from the switching control circuit, wherein a first winding of the transformer is connected to the switching control circuit;
• and
• a demodulator circuit connected to at least one second winding of the transformer and having an output coupled to the gate of the at least one power switching transistor, wherein the output of the demodulator is a gate control signal generated at the switching rate from a control signal received from the at least one second winding at the modulated rate, and wherein the demodulator asserts the gate control signal upon detection of the turn-on event within the modulated control signal.

A method for controlling a switching power stage, comprising:

• generating a modulated control signal for controlling a turn-on time and a turn-off time of at least one power switching transistor of the switching power stage at a switching rate of the switching power stage, wherein the modulated control signal is generated at a modulated rate greater than the switching rate of the switching power stage, rate, wherein the modulated control signal encodes events according to codes specified by relative timing of transitions of the modulated control signal in multiple periods of the modulated control signal, the events including a turn-on event corresponding to the turn-on time of the at least one power switching transistor;
• transformer isolating the modulated control signal to provide a DC isolated control signal to at least one power switching transistor of the switching power stage;
• demodulating the DC isolated control signal from the modulated rate to control the at least one power switching transistor at the switching rate;
• and
• controlling a gate of the at least one power switching transistor in conformity with a result of the demodulating, wherein the at least one power switching transistor is turned on upon detection of the turn-on event, and wherein the at least one power switching transistor is turned off upon detection of another code.

A method for controlling a switching power stage, comprising:

• generating a modulated control signal for controlling a turn-on time and a turn-off time of a transistor of the switching power stage at a switching rate of the switching power stage, wherein the modulated control signal is generated at a modulated rate greater than the switching rate of the switching power stage, wherein the generating encodes one or more event types specified by relative timing between transitions of the modulated control signal, the event types including a turn-on event that indicates the turn-on time of the transistor, and wherein the generating stops generating the transitions of the modulated control signal to conserve power between events;
• transformer isolating the modulated control signal to provide a DC isolated control signal to at least one power switching transistor of the switching power stage;
• demodulating the DC isolated control signal from the modulated rate to control the at least one power switching transistor at the switching rate;
• and
• controlling a gate of the at least one power switching transistor in conformity with a result of the demodulating, wherein the demodulator asserts the gate control signal upon detection of the turn-on event within the modulated control signal.

An integrated circuit, comprising:

• a pair of terminals for connection to an output winding of a transformer having a modulated control signal imposed from an input winding carrying information for controlling a switching power stage, wherein the switching power stage produces a switched power output at a switching rate and includes at least one power switching transistor, wherein the modulated control signal is generated at a modulated rate greater than the switching rate of the switching power stage, wherein the modulated control signal encodes events according to codes specified by relative timing of transitions of the modulated control signal in multiple periods of the modulated control signal, the events including turn-on event corresponding to the turn-on time of the at least one power switching transistor;
• and
• a demodulator circuit having inputs coupled to the pair of terminals and having an output coupled to a driver circuit for controlling the gate of the at least one power switching transistor, wherein the output of the demodulator is a gate control signal generated at the switching rate from a signal received by the pair of terminals from the output winding that contains the information at the modulated rate, and wherein the demodulator asserts the gate control signal upon detection of the turn-on event and de-asserts the gate control signal upon detection of another code.